A tilt type discharge valve for a pressurized container, like that shown in my application Ser. No. 693,768, filed June 8, 1976, now abandoned, has a tiltable, hollow, central valve stem with ports arrayed around the stem and leading into the stem from the pressurized container on which the valve is mounted. The valve stem leads to the outside of the container.
A valve disc or head surrounds the valve stem inside the container. The disc seals against a stationary valve seat held on the body of the valve. With the valve disc held against the valve seat, the entrance ports to the valve stem are closed. When the valve stem and disc are tilted, an arcuate, wedge shaped passageway is made available to the pressurized product to enter the entrance ports of the stem.
On tilting of the stem and the valve head in conventional tilt valves, it is only the foremost ports of the valve stem at the side of the valve head that opens widest that receive the product generally over their full cross-sectional flow areas, whereas the other ports, and particularly the downside ports, are only partially in registry with the wedge-shaped product passageway or space above the valve head. As a result, the total flow cross-sectional area of the ports in the valve stem is not fully utilized. This presents no problem when the contents of the pressurized container are under elevated pressure, as when the container is just starting to be discharged. But, when the contents are near exhaustion and container pressure is low, the reduced flow cross-sectional area of the entrance ports inhibits adequate product flow. One of the reasons that a pressurized container must start with a high internal pressure is to secure an adequate rate of flow into the valve stem, especially when the contents of the container are approaching exhaustion.
Conventional gas pressurized containers have a constant size outlet opening. In conventional gas pressurized containers, it is, therefore, desirable that the container pressure remain substantially constant throughout the entire dispensing of all of the pressurized material, for if the pressure decreases, the flow rate of material dispensed from the container declines.
As the contents of a pressurized container are dispensed, however, the pressurizing gas in the container must fill a greater volume. Usually, this would correspondingly reduce the pressure of the pressurizing gas. This drawback is true of pressurized air. To avoid this, it has become usual to use a pressurizing medium which puts a greater quantity of pressurizing gas into the pressurized container as the volume provided for that gas enlarges. Typically, a liquefiable gas is the medium used, as a charge of such a gas will tend to maintain a continuous pressure in a container as the pressurized contents of the container are gradually expelled. For example, Freon gas is used as the pressurizing medium in many containers. Unfortunately, serious questions have been raised with respect to the environmental hazards associated with Freon gas or other such pressurizing mediums. Accordingly, it has become desirable to develop a valve for a pressurized container which enables effective use of a pressurizing medium, such as air, which is not environmentally dangerous.